Electrical protective apparatus



Filed Dec. 19. 1931 INVENTOR 1 1 Patented June 4, 1935 UNITED STATESPATENT OFFICE George N. ileminon, Homewood, Ala, assignor to SouthernStates Equipment (Company, Birmingham, Ala.

Application December 19, 1931, Serial No. ESZAMI? '3 Claims.

The object of my invention is to provide a combined fuse and lightningarrester which shall be simpler, more easily made, and more effective inoperation than equipment previously made.

Fuse equipment for protecting a transformer is already made with atubular container which is pivoted at one end and so arranged that thetube swings open whenever the fuse link has been ruptured, therebygiving a positive indication that the circuit is open. Also lightningarresters have been used near such fuses, these arresters always beingheld to the cross-arms by separate mountings; and often it is foundadvisable to use additional cross-arms for the arresters.

Arresters are now used which consist merely of a suitable arc gap fromline to ground. The gap is of such spacing that the voltage has to risesubstantially above normal conditions before current will break acrossthe gap. When once broken down, however, the arc offers but littleresistance to the flow of current as the heated gases are highlyconductive. Under such conditions a high voltage surge on the line isdischarged across the gap to ground, and this is followed by a flow ofdynamic current which is in reality a short-circuit to ground. Thisopens the oil circuit breakers and leaves the power supply off the line,so the arc across the gap immediately ceases and is replaced by coolair, restoring normal conditions as soon as the circuit breakers shallhave been closed. The gap is so substantial that it can withstand suchan are without serious damage. To prevent the shortcircuit and theconsequent opening of the breakers and interruption to service, somearresters are made with resistance units in the ground path to limit theflow of dynamic current sufficiently for the arc across the gap to breakthe circuit before the breakers open. Such an arrester will discharge toground the small high frequency surges which otherwise constitute manyof the causes of line trouble. I

Arresters which have resistance members among their elementsare'occasionally so badly damaged by lightning that they ceasev tofunction as arresters, and actually form a path from the line to ground.Such an occurrence interrupts service on the line until the damagedarrester can be disconnected; and it is often difficult to determinewhich of the arresters on a long line is the damaged one.

My arrangement overcomes these objections and provides a device that iscompact and also low in cost.

. an arc across I2, I3, and to cause no blowing of Referring to thedrawing, the figure shows one of my devices in actual service. To across-arm i is clamped the iron support 2 upon which two insulators 3, lare mounted. An insulating tube 5 is pivoted at i and held at its upperend by the latch members I, 8. Inside the tube is the fuse member 9, andwhen this is ruptured the tube automatically drops open to the position5. All this is well known to those familiar with the art. 10

A third insulator I6 is clamped to 2 and contains a resistance element II which forms a current-limiting path between the adjustable airgap I2,I3 and the ground-wire I4. Together these form a path for discharginghigh-frequency small-amperage currents from line to ground.

Occasionally an electric line is subjected to conditions which require amuch heavier discharge to relieve the abnormal voltage. The adjustablehorns I5, I6 give a direct path to 20 ground with no resistance memberin the circuit after the gap has been spanned.

The insulator base I9 and the base member 20 of the horn I6, are held bytwo bolts 2|, so that they clamp tightly about the base member 2. 5 Thisclamp can be adjustably placed upon 2, and adjustment is also providedfor the gap electrodes I2, I3 and I5.

The conductor I1 connects with the main line, and the conductor I8connects with a transformer. The fuse 9 serves the double purpose ofprotecting the transformer and clearing the arrester units In, II, I2,-l3 from the line in case they become short-circuited.

In operation, any small high-frequency surge will be discharged throughthe resistance II as soon as the voltage gets high enough to span theclosely-set gap I2, I3. The resistance II is enough to preventlinecurrent from maintaining the fuse in most cases.

However, a surge sometimes is so heavy that it cannot pass easilythrough the resistance I I and the voltage continues to increase untilit is sufficient to span the gap I5, I6. This relieves all high-voltagesurges which are on the line at this place, and it also usually causesthe oil breaker at the power station to open.

The horns are heavy enough not to be damaged even by such discharge andservice is resumed as soon as the oil breaker is reclosed. Such amomentary interruption is better than to allow the transformers or otherapparatus to be damaged.

If for any reason the close gap I2, I3 should ment within the housing,two arc-gaps each consisting of two spaced electrodes, one electrode ofone arc-gap attached directly to the base, one electrode of the secondarc-gap connected to the high-resistance element, together with oneother electrode for each of the two arc-gaps, one being connected toeach of the said insulated fuse terminals.

2. Electrical protective equipment which includes a base, two fuseterminals insulated from the base, and two arc-gaps, one electrode ofone of the arc-gaps being connected to one of .the

fuse terminals, one electrode of the other aregap being connected to theother terminal, the other electrodesof the two are gaps being connectedtogether through a resistance.

3. As an article of manufacture, a single base supporting two fuseterminals" base, a fuse container supported between the said terminals,an arc-gap between each fuse terminal and the said base, at least one ofthe ,said are gaps being adjustable.

4. As an article of manufacture, a single base supporting two fuseterminals insulated from the base, a fuse container supported betweenthe ulated from the I l aooaaae said terminals, an arc-gap between eachfuse terminal and the said base, and a high-resistance in series withone of the said arc-gaps between a fuse terminal and the base.

. 5. Electrical protective equipment which includes a metal basesupporting two spaced ter minals each insulated from the basei acontainer and a fuse within it connecting the said terminals, adischarge arc-gap between each of the said terminals and the said base,and a resistance forming part of the discharge path from one theterminals across the gap to the base.

6. Electrical protective equipment which includes a metal basesupporting two spaced terminals each insulated from the base, acontainer and a fuse within it connecting the said terminals, adischarge arc-gap between each of the said terminals and the said base,a resistance forming part of the discharge path from one of theterminals across the gap to the base, and a metallic conducting path inseries with the arc-gap which is between the second of the saidterminals and the base.

7..Electrical protective equipment/which includes a metal basesupporting two spaced terminals insulated from the base, a container anda fuse within it connecting the said insulated terminals, a ground, adischarge arc-gap between each of the said terminals and ground, theconductive part of the path from terminal to ground in series with onearc-gap being of substantialy higher resistance than the conductive partof the path from terminal to ground inseries with the other arc-gap.

. GEORGE N. LEMMON.

